1. Technical Field
An aspect of the present invention relates to an image reading apparatus.
2. Related Art
An image reading apparatus, which is equipped with a one-dimensional image sensor, to read an original image appearing on an original sheet, such as an image scanner, a facsimile machine, and a multifunction peripheral device, is known.
In an image reading operation in the image reading apparatus, a process called shading correction is performed prior to actually reading the original image by the image sensor. In the shading correction process, the image sensor reads a reference image (e.g., a solid white image), which is to be recognized as an image with even luminosity, and corrects unevenness of the luminance, if recognized any, amongst pixels contained in the reference image.
When the image reading apparatus is exposed to intense external light such as natural sunlight, the intense light may pass through or may be reflected on parts of the image reading apparatus, and light receiving elements in the image sensor may be exposed to sense the transmissive or reflecting light. Thus, with the interference of the incident light, the uneven shading in the image sensor may not suitably be corrected.
In order to reduce the influence of the incident light, a light-blocking upright bulkhead may be arranged in the image reading apparatus in a vicinity of the image sensor. For example, the light-blocking bulkhead may be arranged in a bottom area of a casing accommodating an optical unit in the image reading apparatus whilst the external light may enter through a part of a platen glass, on which no original sheet is placed.